The present invention relates to a mode switching device by which a limited number of terminals such as external terminals of an integrated circuit (IC) device may be used commonly for different signal processings.
In Japan there is a great demand for tape recorders of the touch button type in which operation buttons are used for different operation modes, respectively. In foreign countries, particularly in the U.S.A. and European countries, the major demand is for tape recorders of the slide button type in which a single button can select a plurality of operation modes. A recent increasing demand is for microcassette tape recorders of the logic control type. The logic circuit for the logic control is generally integrated into a large scale integrated circuit (LSI) of one chip for the reason that the space to accommodate it is restrictive and the manufacturing cost reduction for mass production must be realized. The signals applied to the control LSI of the touch button type tape recorder are different from those used in the slide button type tape recorder. In the touch button type tape recorder, the respective operation buttons are in the ON state only when depressed while they are in the OFF state normally. As a conventional measure for this, latch circuits are provided for the respective operation buttons, for the purpose of temporarily storing the depression of the operation button. In the case of the slide button type device, a switch corresponding to the position of the operation button is continuously depressed, with no need for the storing function by the latch circuit.
As described above, the input signal states, or the input modes, of the LSI are different in accordance with the input signals used. Therefore, when a circuit adaptable for the two kinds of the input modes is designed by using a single LSI, the number of the external terminals of the LSI is extremely increased. The cost of the LSI depends largely on the number of the external terminals. Further, when the number of the external terminals is increased, the size of the LSI is increased. This makes it difficult to reduce the size of the tape recorder. For this reason it is undesirable that the number of the terminals is increased with the increase of the kinds of the input modes.